Low oxygen levels in the bay could stifle marine life this summer

Algae blooms a precursor of `dead' zone, experts say

April 08, 2004|By Lynn Anderson | Lynn Anderson,SUN STAFF

Department of Natural Resources scientists have identified unusually large algae blooms in sections of the Chesapeake Bay that could choke marine life this summer and create the largest oxygen-deprived "dead" zone on record.

Although scientists are unsure exactly what effect the blooms will have in the long term or how bad the summer "dead zone" could be, they said they have never seen dissolved-oxygen levels so low this early in the year since 1986.

The Chesapeake Bay Foundation went public with the findings at a news conference in Annapolis yesterday as part of a lobbying effort for the so-called "flush tax" that would raise funds to curb nutrient pollution from sewage plants.

"This is a precursor of a very severe dead zone, probably this summer," said foundation President William C. Baker.

If water conditions continue to decline, he said, the potential is there for a dead zone larger than last year's, which covered about 40 percent of the bay.

The consequences could be devastating for marine life.

On the other hand, the algae blooms - possibly a type of algae called heterocapsa that thrives in the winter and dies off as water temperatures warm - could dissipate and oxygen levels could improve, Baker said.

"Some scientists are calling this an exception," he said. "We don't want to say this is the end of the world ... but this is an indication that we could be in real trouble this summer."

Scientists are unclear exactly what is causing the large blooms, which can turn the water a mahogany color. Some speculate that the past year's heavy rains could be the culprit.

"It's possible that a lot of organic material washed into the bay [last year] and now it is just getting warm enough to cause this algae to bloom in greater number," said David Goshorn, chief of the living resource assessment program for the Maryland Department of Natural Resources. "But that's speculation at this point."

Goshorn said test results are not back on nutrient and algae samples and it could be several weeks before the cause of the algae blooms is determined. Still, he said, the results so far are worrisome.

"The bottom line is that in the main stem of the bay we are seeing near record-low and record-low levels of dissolved oxygen," he said. "Although the [dissolved-oxygen] levels are not low enough yet to cause stress or death to fish, the levels are low for this time of the year."

Goshorn oversees scientists who test water samples to track dissolved-oxygen levels. The more dissolved oxygen, the healthier the bay is for marine life. When large doses of nitrogen and phosphorus are introduced, algae colonies proliferate. When algae dies, it uses up oxygen as part of its decay process. Less oxygen is tougher on fish, crabs and oysters.

Large "dead zones" make it difficult for fish and crabs to swim to more oxygenated water, resulting in fish kills and crab "jubilees," where crabs are seen thrashing on the surface.

An analysis of data collected from 54 state monitoring stations on the bay shows dissolved oxygen at below-average levels for this time of the year, according to the Chesapeake Bay Foundation.

Of those, 10 stations, many of them on some of Maryland's most popular estuaries, including the South, Severn and Chester rivers, posted record lows.

Only three unnamed stations posted improved dissolved-oxygen levels.

While the effects of lower oxygen levels this early in the year are unknown, watermen have reported for the first time seeing rockfish wintering on the Susquehanna Flats rather than in deeper waters where they typically live, said John Surrick, a spokesman for the Chesapeake Bay Foundation. The fish may have moved to find oxygen-rich waters, he said.

River-keepers on the South and Chester rivers said they have also noticed changes in the waterways they guard.

Eileen McLellan, who watches over the Chester River, said dissolved-oxygen levels in the lower river reached record lows for March. She is organizing volunteers to perform regular water tests throughout the summer.

"This is about as bad as it can get," she said. "What does this mean for the summer?"

Drew Koslow, who monitors the South River, said he has taken water samples near a "pretty severe" algae bloom and is awaiting the results.

"We are worried," he said. "Typically we have algae blooms at the headwaters of the river, and we expect that, but this is really unusual."